In the hypothalamus, histamine is released according to a circadian rhythm. Peak releases of histamine occur during the night together with enhanced locomotion. These observations have led to the idea that brain histamine is implicated in arousal mechanisms and that, in the posterior hypothalamus, histamine released from its neurons contributes to wakefullness and increased locomotion in the night. Additionally, in the rat hypothalamus histamine is released according to an ultradian rhythm. Ultradian fluctuations have also been observed in the theta and delta frequency bands of the EEG spectral power. Simultaneous recordings of histamine outflow and EEG in the hypothalamus revealed that the ultradian histamine release rhythm coincides timely with ultradian fluctuations in the EEG spectral power. It is noteworthy, that histamine receptor ligands used in pharmacotherapy, like H1 and H2 antagonists, influence the frequency of the EEG spectral power fluctuations. It is not clear, whether these changes in the fluctuation frequency of the EEG spectral power have concequences for patients treated with the drugs. Brain histamine also seems to be involved in memory processes. Central administration of H3 agonists deteriorates, while H3 antagonists improve short-term memory. The latter finding may open new horizons in pharmacological treatment of memory disorders.

Back to the top.Presentation Number SAphilippu0262Keywords:Histamine, Push-pull, EEG Power, Rhythms, Memory